How it works
Choose metric or imperial, enter your height and weight, and hit Calculate my BMI. Body Mass Index is your weight in kilograms divided by the square of your height in metres — one number that screens for weight-related health risk in adults.
What your BMI means
These are the standard adult categories used worldwide. They apply to ages 18 and above.
| BMI | Category | What it suggests |
|---|---|---|
| Below 18.5 | Underweight | May reflect under-nutrition or naturally slight build. Unintentional weight loss deserves a doctor’s visit. |
| 18.5 – 24.9 | Healthy weight | The range linked with the lowest health risk for most adults. |
| 25 – 29.9 | Overweight | Above the healthy range. Even modest, sustained weight loss improves blood pressure, blood sugar and cholesterol. |
| 30 and above | Obese | Higher risk for diabetes, heart disease and joint problems. A doctor can assess the full picture and plan next steps. |
What BMI does not tell you
BMI is a screening number, not a body scan. It cannot distinguish muscle from fat, so athletes and muscular workers can score high while being healthy. It also misses where fat sits — belly fat around the organs carries more risk than the same weight on hips and thighs, which is why doctors often measure waist circumference alongside BMI.
Age matters too: older adults naturally lose muscle, so the same BMI can mean more body fat at 70 than at 30. And during pregnancy, BMI is not used at all. Treat your result as a starting point for a conversation with your doctor, not a verdict.